1. Field of the Invention
The present invention relates to a turbocharger system and a control method for the same.
2. Description of the Related Art
Turbochargers have been known as being used to increase output of engines and the like by being connected thereto. As boost pressure of a turbocharger becomes higher, the subsequent flow rate and pressure of the exhaust gas become higher. As the torque of the turbocharger becomes higher, the boost pressure becomes much higher. As a result, the engine and the turbocharger become more likely to suffer damage. To avoid this, some turbocharges have a function of suppressing the pressure of the exhaust gas flowing into a turbine housing by making part of the exhaust gas flow from the engine to the downstream of the turbine while bypassing the turbine.
A turbocharger having the foregoing function is provided with a bypass passage making the upstream and downstream of a turbine impeller communicate with each other. The turbocharger is further provided with a wastegate valve configured to open and close the bypass passage. Depending on the pressure in a compressor housing, the valve lift (a degree of opening) of the wastegate valve is adjusted by an actuator connected to the wastegate valve.
As the shape of the turbocharger changes with time, the relative positions of the wastegate valve and a hole to be closed by the wastegate valve also change. For this reason, the actuator, if electrically operated, becomes no longer capable of adjusting the opening of the hole appropriately even when controlling the wastegate valve. Japanese Patent No. 4434057 (PTL 1) has proposed a turbocharger having a function of resetting the relationship between the control amount and the valve lift of the wastegate valve when necessary.